The following background is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art to the present invention.
Caffeine is a bitter substance that acts on many humans as a central nervous system stimulant, temporarily warding off drowsiness and restoring alertness. It is the most widely used of all psychoactive drugs. Caffeine consumption from all sources has been estimated at around 70 to 76 mg/person/day worldwide and about 210 to 238 mg/day in the US and Canada. In North America, 90% of adults consume caffeine daily. Daily caffeine consumption may reach a value of 2.4 to 4.0 mg/kg (170-300 mg) in a 60- to 70-kg individual, largely from coffee, tea, soft drinks, energy drinks, and chocolate foods. A cup of coffee, a soft drink or an energy drink can have about 80-200 mg, 30-60 mg or 60-280 mg caffeine per serving, respectively.
Caffeine is a hydrophobic compound with relatively low solubility in water. The absorption of caffeine by the oral route, from the gastrointestinal tract, is rapid and reaches 99% in humans in about 45 minutes after ingestion. However, the oral route has disadvantages. The consumption of caffeine via soft drinks, energy drinks and chocolate foods contributes to weight gain and obesity. The consumption of caffeine from coffee and tea contributes to stomach aches and gastrointestinal disorders. Withdrawal symptoms after the discontinuation of caffeine from one's diet may include headache, irritability, inability to concentrate, drowsiness, insomnia, and pain in the stomach.
Therefore, improved formulations of caffeine are needed. Also needed is an efficient means to administer caffeine more directly into the blood steam, relative to the oral route and without the concomitant consumption of foods and beverages that contain caffeine. For example, it would be desirable to provide improved methods and compositions for the pulmonary delivery of caffeine. Although caffeinated powders have been developed for inhalation, these powders are ineffective because they settle on the tongue, mouth and throat of a subject where they are substantially rinsed into the stomach for oral delivery.
Personal electronic vaporizers such as electronic cigarettes have been developed for the pulmonary administration of relatively small concentrations of active compounds. Electronic cigarettes, which generally include a battery, vaporizer (i.e., atomizer), chamber to store the liquid and a mouthpiece, have been used to effectively vaporize actives such as nicotine for pulmonary administration. The quantity of nicotine delivered by electronic cigarettes ranges from “low” doses of about 6-8 μg to “ultra high” doses of about 36-48 μg.